that isn't something up for debate. it is part of the mcu, period. not considering tih part of the mcu is just the same as not considering iron man, or the first avenger, or thor, or guardiands of the galaxy in the mcu.I consider TIH canon, because it was really the second MCU movie. RDJ even shows up in the post credit scene. AngHulk is debateable, but I would put it as occurring before IM1 if I was counting it.
...the proof is tih being the second film of the mcu. anybody doubting it is kidding themselves.William Hurt's General Thunderbolt Ross from TIH is showing up in Civil War, so that's further proof that TIH is canon.